Date:   Mon, 05 Mar 2018 00:46:00 -0800
From:   syzbot <syzbot+41acdbdb481f47bd942a@...kaller.appspotmail.com>
To:     coreteam@...filter.org, davem@...emloft.net, fw@...len.de,
        kadlec@...ckhole.kfki.hu, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        pablo@...filter.org, syzkaller-bugs@...glegroups.com
Subject: INFO: task hung in get_info

Hello,

syzbot hit the following crash on upstream commit
4a3928c6f8a53fa1aed28ccba227742486e8ddcb (Mon Feb 26 02:50:41 2018 +0000)
Linux 4.16-rc3

So far this crash happened 8 times on net-next, upstream.
Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+41acdbdb481f47bd942a@...kaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

Buffer I/O error on dev loop0, logical block 0, async page read
INFO: task syz-executor7:4237 blocked for more than 120 seconds.
       Not tainted 4.16.0-rc3+ #330
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D22160  4237      1 0x00000004
Call Trace:
  context_switch kernel/sched/core.c:2862 [inline]
  __schedule+0x905/0x2070 kernel/sched/core.c:3440
  schedule+0xf5/0x430 kernel/sched/core.c:3499
  schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3557
  __mutex_lock_common kernel/locking/mutex.c:833 [inline]
  __mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893
  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
  xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
  xt_request_find_table_lock+0x28/0xc0 net/netfilter/x_tables.c:1087
  get_info+0x154/0x690 net/ipv6/netfilter/ip6_tables.c:993
  do_ip6t_get_ctl+0x159/0xaf0 net/ipv6/netfilter/ip6_tables.c:1714
  nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
  nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
  ipv6_getsockopt+0x1d5/0x2c0 net/ipv6/ipv6_sockglue.c:1370
  tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3359
  sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2934
  SYSC_getsockopt net/socket.c:1880 [inline]
  SyS_getsockopt+0x178/0x340 net/socket.c:1862
  do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45683a
RSP: 002b:0000000000a3e3b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000a3e3e0 RCX: 000000000045683a
RDX: 0000000000000040 RSI: 0000000000000029 RDI: 0000000000000013
RBP: 00000000006fd720 R08: 0000000000a3e3dc R09: 0000000000004000
R10: 0000000000a3e3e0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000013 R14: 0000000000000029 R15: 00000000006fb560

Showing all locks held in the system:
2 locks held by khungtaskd/794:
  #0:  (rcu_read_lock){....}, at: [<00000000f2e23315>]  
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
  #0:  (rcu_read_lock){....}, at: [<00000000f2e23315>] watchdog+0x1c5/0xd60  
kernel/hung_task.c:249
  #1:  (tasklist_lock){.+.+}, at: [<00000000e9297713>]  
debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470
1 lock held by rsyslogd/4040:
  #0:  (&f->f_pos_lock){+.+.}, at: [<0000000082cca4c6>]  
__fdget_pos+0x12b/0x190 fs/file.c:765
2 locks held by getty/4162:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005f2fb7f7>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000004c165f9>]  
n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131
2 locks held by getty/4163:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005f2fb7f7>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000004c165f9>]  
n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131
2 locks held by getty/4164:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005f2fb7f7>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000004c165f9>]  
n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131
2 locks held by getty/4165:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005f2fb7f7>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000004c165f9>]  
n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131
2 locks held by getty/4166:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005f2fb7f7>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000004c165f9>]  
n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131
2 locks held by getty/4167:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005f2fb7f7>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000004c165f9>]  
n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131
1 lock held by syz-executor7/4237:
  #0:  (&xt[i].mutex){+.+.}, at: [<0000000005236191>]  
xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
1 lock held by syz-executor4/4242:
  #0:  (&xt[i].mutex){+.+.}, at: [<0000000005236191>]  
xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
1 lock held by syz-executor6/4244:
  #0:  (&xt[i].mutex){+.+.}, at: [<0000000005236191>]  
xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
1 lock held by syz-executor5/4245:
  #0:  (&xt[i].mutex){+.+.}, at: [<0000000005236191>]  
xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
1 lock held by syz-executor1/4247:
  #0:  (&xt[i].mutex){+.+.}, at: [<0000000005236191>]  
xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
1 lock held by syz-executor2/23072:
  #0:  (&xt[i].mutex){+.+.}, at: [<0000000005236191>]  
xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
2 locks held by getty/32490:
  #0:  (&tty->ldisc_sem){++++}, at: [<000000005f2fb7f7>]  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<0000000004c165f9>]  
n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131
1 lock held by syz-executor3/10669:
  #0:  (&xt[i].mutex){+.+.}, at: [<00000000f378abbd>]  
xt_find_target+0x44/0x1e0 net/netfilter/x_tables.c:231
1 lock held by syz-executor3/10671:
  #0:  (&xt[i].mutex){+.+.}, at: [<00000000f378abbd>]  
xt_find_target+0x44/0x1e0 net/netfilter/x_tables.c:231

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 794 Comm: khungtaskd Not tainted 4.16.0-rc3+ #330
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x24d lib/dump_stack.c:53
  nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
  nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:62
  arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
  trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
  check_hung_task kernel/hung_task.c:132 [inline]
  check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
  watchdog+0x90c/0xd60 kernel/hung_task.c:249
  kthread+0x33c/0x400 kernel/kthread.c:238
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:407
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6909 Comm: syz-executor0 Not tainted 4.16.0-rc3+ #330
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:match_held_lock+0xcb/0x880 kernel/locking/lockdep.c:3495
RSP: 0018:ffff8801af8ef4f8 EFLAGS: 00000046
RAX: 0000000000000003 RBX: 1ffff10035f1dea4 RCX: 0000000000000006
RDX: 0000000000000000 RSI: ffffffff86f42800 RDI: ffff8801d4ff2c9a
RBP: ffff8801af8ef5e8 R08: 1ffff10035f1dea7 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d4ff2400
R13: ffff8801d4ff2c78 R14: 0000000000000000 R15: ffff8801af8ef5c0
FS:  000000000138c940(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbde502e000 CR3: 00000001cdb7c003 CR4: 00000000001626e0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
  __lock_is_held+0xb6/0x140 kernel/locking/lockdep.c:3740
  lock_is_held_type+0x118/0x210 kernel/locking/lockdep.c:3958
  lock_is_held include/linux/lockdep.h:344 [inline]
  rcu_preempt_sleep_check include/linux/rcupdate.h:301 [inline]
  ___might_sleep+0x35e/0x470 kernel/sched/core.c:6098
  htable_selective_cleanup+0x29c/0x3d0 net/netfilter/xt_hashlimit.c:381
  htable_destroy net/netfilter/xt_hashlimit.c:415 [inline]
  htable_put+0x1de/0x300 net/netfilter/xt_hashlimit.c:442
  hashlimit_mt_destroy+0x56/0x70 net/netfilter/xt_hashlimit.c:979
  cleanup_match+0x14e/0x220 net/ipv6/netfilter/ip6_tables.c:485
  cleanup_entry+0xef/0x380 net/ipv6/netfilter/ip6_tables.c:669
  __do_replace+0x7ac/0xa70 net/ipv6/netfilter/ip6_tables.c:1112
  do_replace net/ipv6/netfilter/ip6_tables.c:1168 [inline]
  do_ip6t_set_ctl+0x40f/0x5f0 net/ipv6/netfilter/ip6_tables.c:1690
  nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
  nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
  ipv6_setsockopt+0x10b/0x130 net/ipv6/ipv6_sockglue.c:927
  tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2905
  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2975
  SYSC_setsockopt net/socket.c:1849 [inline]
  SyS_setsockopt+0x189/0x360 net/socket.c:1828
  do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45685a
RSP: 002b:0000000000a3e3b8 EFLAGS: 00000206 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000a3e3e0 RCX: 000000000045685a
RDX: 0000000000000040 RSI: 0000000000000029 RDI: 0000000000000013
RBP: 00000000006fd720 R08: 00000000000002e8 R09: 0000000000004000
R10: 00000000006fc940 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000013 R14: 0000000000000029 R15: 00000000006fc9a0
Code: 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0  
01 38 d0 7c 08 84 d2 0f 85 9d 04 00 00 66 41 f7 45 22 f0 ff <0f> 84 f9 01  
00 00 48 8d 7e 08 48 b8 00 00 00 00 00 fc ff df 48


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@...glegroups.com.

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